Effect of platelet agonists on airway reactivity and intrathoracic platelet accumulation

1 Intravenous infusion of platelet activating factor (Paf), adenosine diphosphate (ADP), collagen and the thromboxane-mimetic U46619 induced a dose-related accumulation of 111indium-labelled platelets into the thoracic region of anaesthetized guinea-pigs. 2 Intravenous infusion of Paf increased the reactivity of the airways to the spasmogen histamine. Such changes were not observed following treatment with ADP, collagen or U46619. 3 Paf-induced bronchial hyperreactivity is not secondary to pulmonary platelet recruitment, changes in basal lung function or cardiovascular changes. 4 Paf-induced bronchial hyperreactivity is not dependent upon the endogenous generation of ADP or thromboxane.